HEAT-SHOCK INCREASES TURNOVER OF 90 KDA HEAT-SHOCK PROTEIN PHOSPHATE GROUPS IN HELA-CELLS

The 90 kDa heat shock protein (hsp90) is a major phosphoprotein which associates various other cellular polypeptides such as actin, calmodulin, steroid hormone receptors and certain protein-kinases. Little is known about the function of hsp90 in recovery from stress. In this report, we describe a dramatic increase in the rate of both phosphate uptake and dephosphorylation of hsp90 in HeLa cells submitted to acute stresses. This increased turnover of hsp90 phosphate groups might reflect a greater protein binding activity of hsp90 in stressed cells.